Preheat oven to 325°F (160°C)—line 4 cookie sheets with parchment paper or use a silicone mat.
Heat the walnuts, butter, flour, and milk in a medium saucepan over medium heat, stirring constantly, until the butter is melted and the ingredients are totally blended.
1 Cup walnuts, ½ Cup unsalted butter, ½ Cup Sugar, 2 Tablespoons all-purpose flour, 2 Tablespoons Milk
Drop a rounded half-teaspoon of mixture onto the cookie sheet, three inches apart.
Bake 12-15 minutes until the cookies are light golden brown. Let them cool for about 5 minutes, then carefully remove them from the parchment paper.
Place the cookies on a cooling rack and cool completely.
For the Filling
Melt the chocolate, butter, and milk in a double boiler. Do not let the water in the bottom pan touch the top pan.
Spread the chocolate on the back side of one cookie. Top with a cookie of similar shape and size. It’s best to lay the cookies on a flat table since they are very fragile. Don’t push down too hard with the spreading knife because that can crack the cookie, too.
Notes
Pro Tips
Let the cookie dough cool off for a couple of minutes after melting. It doesn't spread as much.
Shape the dough into rounds; if they are oddly shaped, the cookies will be too.
Be sure that your oven temperature is correct. These cookies burn easily.
Handle the cookies carefully, as they are very delicate.
Some recipes add oats to the dough, which helps with their delicate nature but does not reflect this version. This version has a distinct toffee-like flavor and a delightful crispy texture.
Use real unsalted butter for this recipe. Margarine will not produce a satisfactory flavor.
Either store these cookies at room temperature or freeze them for longer storage. The humidity from the refrigerator will render them soggy.
These cookies can be made gluten-free easily. Just substitute almond flour for the all-purpose flour in the recipe.